1. Field of the Invention
This invention relates to a thin film lens formed of semiconductors, and more particularly to a thin film lens suitable for condensing a laser light emitted from a semiconductor laser or the like.
2. Description of the Prior Art
Generally, the light emitted from a semiconductor laser is an asymmetrical elliptical beam having great angles of expanse of 30.degree.-60.degree. in a direction perpendicular to the joined surface and 4.degree.-10.degree. in a direction parallel to the joined surface. Therefore, where the light beam from a semiconductor laser, for example, is provided directly to a light waveguide or an optical fiber, the coupling efficiency is remarkably reduced. Therefore, use has heretofore been made of a coupling system as shown in FIGS. 1A and 1B of the accompanying drawings. FIG. 1A is a schematic cross-sectional view of the coupling system, and FIG. 1B is a plan view of the coupling system. The asymmetrical beam 4 emitted from a semiconductor laser 1 is made into a symmetrical beam 4' by a minute diameter cylindrical lens 2 and directed into an optical fiber 3. Reference numeral 5 designates a heat sink, and reference numeral 6 denotes a support jig. To obtain sufficient coupling efficiency in such a coupling system, the optic axes of the lens and the optical fiber must be exactly coincident with the light beam.
However, the diameter of the aforementioned minute diameter cylindrical lens is as small as 0.2-0.3 mm and the coupling efficiency is remarkably reduced for any deviation from the optic axis, and this has led to a disadvantage that position adjustment of the lens is very difficult.
Also, generally in a case where a lens is to be incorporated into an optical integrated circuit including a semiconductor laser or the like, adjustment of the optic axis thereof and fixing of the lens is difficult, and this has formed a factor which hampers the integration.